Lubricant for magnetic disks, method for producing the lubricant used in the magnetic disks, and method for manufacturing the same
View Patent ↗The present invention provides a lubricant for forming a lubricating layer which is useful in preventing fly and stiction and/or corrosion at an extremely small flying height of 10 nm or less, which is prevented from migrating at a high rotational speed of 5400 rpm or more, which has high adhesion, and which is suitable for a load/unload method. A crude lubricant containing at least one perfluoropolyether is degassed and then purified. Alternatively, a liquid crude lubricant containing at least one perfluoropolyether is purified by vaporizing the crude lubricant and then liquefying the vapor of the perfluoropolyether within a distance less than the mean free path of molecules of the perfluoropolyether. A magnetic disk is prepared in such a manner that a carbonaceous protective layer is formed above a substrate and a lubricating layer is formed on the protective layer using of the lubricant. The lubricant contains the perfluoropolyether and has a molecular weight distribution of 1.3 or less.
1. A lubricant for use in manufacturing a magnetic disk, comprising a compound represented by the following formula:
wherein the lubricant is prepared by a method comprising the following steps:
preparing a crude lubricant which includes at least the compound;
heating the crude lubricant to a temperature of 160° C. to 200° C.;
degassing an impurity gas from the crude lubricant in a reduced pressure;
after the degassing, vaporizing a degassed lubricant into a vaporized lubricant; and
purifying the vaporized lubricant into the lubricant by liquefying the compound molecules of the vaporized lubricant within a distance less than a mean free path of the compound molecules.
2. A magnetic disk comprising at least a magnetic layer, a protective layer, and lubricant layer which are formed on a substrate, wherein the lubricant layer comprises the lubricant according to claim 1 .
3. The lubricant for use in manufacturing a magnetic disk according to claim 1 , wherein the compound comprises at least 85 mole percent of the lubricant, as measured by nuclear magnetic resonance spectroscopy.
4. The lubricant for use in manufacturing a magnetic disk according to claim 1 , wherein the compound comprises between 90 and 95 mole percent of the lubricant, as measured by nuclear magnetic resonance spectroscopy.
5. The lubricant according to claim 1 , in which the molecular weight distribution is not smaller than 1.0 and is not greater than 1.3, and in which the weight-average molecular weight is between 4000 and 8000.
6. The magnetic disk according to claim 2 , wherein the compound comprises at least 85 mole percent of the lubricant, as measured by nuclear magnetic resonance spectroscopy;
the molecular weight distribution of the lubricant is not smaller than 1.0 and is not greater than 1.3; and
the weight-average molecular weight of the lubricant is between 4000 and 8000;
wherein the lubricant layer is formed by dip coating.
7. The magnetic disk according to claim 6 , wherein the compound comprises between 90 and 95 mole percent of the lubricant, as measured by nuclear magnetic resonance spectroscopy.
8. The magnetic disk according to claim 6 , wherein the bonded ratio is greater than 80%.
9. The magnetic disk according to claim 6 , wherein the bonded ratio is between 82 and 85%.
10. The magnetic disk according to claim 6 , installed in a magnetic disk drive of a load/unload type.
11. The magnetic disk according to claim 10 , installed in the magnetic disk drive which comprises a magnetic head including a negative pressure slider.